How do I configure wordpress network to use subdomains?

I think I need to have both my site url and wordpress url with a www prefix, if I don’t, I can’t log in to my site because if I try to open just the ‘domain’ only, ie domain.com, my page is redirected to a www anyway. I have a clean htaccess file, my dns doesn’t yet have the wildcard for subdomains. But I think for a subdomain network I need just the domain as site url, right? I realise there are probably a few issues here. I think the key thing to get settled is what I add as site url. Oh my wordpress is the latest version – 3.6.1 I think. It’s possible that my server is incorrectly configured, I’ve asked my hosts to check it out too, but it would be great if someone who has installed WP Network on subdomains could give me a few pointers. Thanks